1. Field of Invention
This invention relates to solvent extraction of fats and/or oils from products containing fats and/or oils, wherein the extraction solvent is a liquefied gas.
2. Description of Related Art
A variety of methods have been developed for extracting edible fats and oils from materials containing them. These methods fall into two classes: (1) mechanical extraction methods; and (2) solvent extraction methods. Mechanical extraction methods employ pressure to squeeze fats and oils from oleaginous materials. Solvent extraction methods separate fats and oils from oleaginous materials by contacting the oleaginous materials with a solvent in which fats and oils are more soluble than other components of the oleaginous materials, separating the solvent and fat/oil solution (i.e., miscella) from the defatted material and separating the fat/oil from the solvent.
Extraction methods have been employed to extract edible fats and oils from a wide variety of materials, including animal flesh, oilseeds and plant matter, such as cereal brans, fruits, beans and nuts. See, e.g., U.S. Pat. No. 1,802,533 to Reid, U.S. Pat. No. 2,560,935 to Dickinson, U.S. Pat. No. 5,041,245 to Benado, U.S. Pat. No. 5,980,964 to Walters et al., U.S. Pat. No. 6,066,350 to Purtle et al. and U.S. Pat. No. 6,111,119 to Trout.
For example, cocoa beans are processed to obtain cocoa butter and cocoa powder. Cocoa butter represents a portion of the fat content isolated from the cocoa beans. The cocoa powder represents solids remaining after processing to recover cocoa butter.
In typical processing, the cocoa beans are harvested within a husk. Typically, the beans are dried in the fields, and then dehusked. The beans are then subjected to various forms of heating, for example, intense infrared treatment, to pop the shells and in some instances for microbiological control. The shelled beans are generally referred to as cocoa nibs. The nibs are separated from the shells for processing.
In typical processing operations, the nibs are roasted and in some instances subjected to dutching (alkali treatment or alkalization). The nibs are then ground, often with significant generation of heat.
In general, the mass which results from grinding of the nibs is referred to as xe2x80x9ccocoa massxe2x80x9d, xe2x80x9ccocoa liquorxe2x80x9d or xe2x80x9cchocolate liquorxe2x80x9d. At room temperature, it is a thick solid mass; however, when heated above the melting point of the fat it forms a viscous, flowable slurry. Typical cocoa liquors contain about 50-58 wt. % fat and 42-50 wt. % powder (or remaining solids). The fat content of cocoa liquor is that portion generally referred to as xe2x80x9ccocoa butterxe2x80x9d, after it has been separated from the remainder of the mass.
In conventional mechanical or xe2x80x9cpressxe2x80x9d processing, chocolate liquor is mechanically pressed, to physically squeeze a portion of the fat out. In some instances the mass may be washed, to modify flavor or color. Generally up to about 80-85 wt. % of the fat content (of the 50-60 wt. %) can be removed from the cocoa mass by mechanical pressing. This typically leaves a cake comprising about 10-20 wt. % cocoa butter (often 11-12 wt. %), by weight, the remainder comprising cocoa powder. Cocoa powder with a fat content of about 10 wt. % or below is often referred to as low-fat cocoa powder. The fat which is isolated by mechanical pressing is typically called xe2x80x9cpress butterxe2x80x9d. The time and pressure it takes to remove the fat by pressing increases substantially when the process is practiced to reduce the residue cake from about 20 wt. % fat content to about 11 wt. % fat content or lower. In addition, mechanical press extraction tends to increase the likelihood of bacterial contamination.
Cocoa beans have been processed by pressing generally in the manner described above for many decades to produce two principal commoditiesxe2x80x94the cocoa butter isolated from the pressing steps and the cocoa powder (typically containing about 10-20 wt. % cocoa fat by weight).
In some applications, the fat content (10-20 wt. %) of the cocoa powder has been found undesirable. Such applications include those in which it is desired that the ultimate food product which is manufactured contain relatively low amounts of various added fats or oils. In recent years, then, processes of reducing the fat content of cocoa powder have been examined.
In general, fat-free cocoa powders, i.e., cocoa powders containing no more than about 0.5% by weight cocoa butter, have been produced by extracting the cocoa powder obtained after pressing, via solvent extraction. Hexane and carbon dioxide, for example, have been used to extract cocoa butter from cocoa feedstocks, but have been less than totally satisfactory. Although hexane is a liquid at room temperature and pressure, having a boiling point well above atmospheric pressure, it has been classified as a hazardous air pollutant under the Clean Air Act, and has been implicated as a neurotoxin. Carbon dioxide extraction of cocoa butter can require large investments in systems capable of withstanding the high pressures required by extraction with carbon dioxide in its supercritical fluid state.
Despite the foregoing developments, it is desired to provide a system for extracting greater amounts of fats and/or oils from materials containing fats and/or oils than has been practical with mechanical pressing systems.
It is also desired to provide an extraction system in which toxic solvents are avoided and flammable solvents are employed safely and effectively.
It is further desired to provide an extraction system in which the capital expenditures for construction are less than those for constructing mechanical press systems and supercritical carbon dioxide fluid extraction systems.
It is still further desired to provide an extraction system in which the operating costs are less than those of mechanical press systems.
All references cited herein are incorporated herein by reference in their entireties.
The invention provides a process for extracting a fat from a feedstock, said process comprising:
mixing said feedstock with a solvent to form a primary slurry of feedstock solids suspended in a primary miscella comprising said solvent and said fat extracted from said feedstock, wherein said solvent is a liquefied gas;
filtering said primary slurry to provide: (a) at least one primary filter cake comprising said feedstock solids and a retentate portion of said primary miscella, and (b) a primary filtrate comprising a filtrate portion of said primary miscella;
washing said at least one primary filter cake with an additional amount of said solvent to form a cake wash slurry comprising said feedstock solids suspended in a secondary miscella comprising said additional amount of said solvent and an amount of said fat extracted from said feedstock;
filtering said cake wash slurry to provide: (a) at least one secondary filter cake comprising said feedstock solids, and (b) a secondary filtrate comprising said secondary miscella;
drying said at least one secondary filter cake with a solvent vapor to provide at least one dried filter cake, wherein said solvent vapor comprises said solvent in a gaseous form;
granulating said at least one dried filter cake to form a defatted powder;
feeding said defatted powder into an oxygen-containing atmosphere at a feed rate to remove at least a portion of a residual amount of said solvent remaining in said defatted powder and provide a powder product, wherein said feeding is regulated to avoid providing a flammable concentration of said solvent in said oxygen-containing atmosphere; and
separating said solvent from said fat in said primary miscella to provide a fat product,
wherein said mixing, said primary slurry filtering, said washing, said cake wash slurry filtering, said drying, and said granulating are conducted under an atmosphere consisting essentially of said solvent vapor.
Further provided is a solvent extraction process comprising loading into an extractor a first batch including a feedstock and a solvent, extracting into said solvent a fat from said feedstock, unloading from said extractor said first batch after said extracting, and repeating said loading, said extracting and said unloading at least once, wherein a pressure in said extractor is continuously maintained above atmospheric pressure (i.e., above about 101.3 kPa and preferably above about 40 psig/276 kPa) throughout said loading, said extracting, said unloading and said repeating.
Still further provided is a solvent extraction process comprising loading into an extractor a first batch including a feedstock and a solvent, extracting into said solvent a fat from said feedstock, unloading from said extractor said first batch after said extracting, and repeating said loading, said extracting and said unloading at least once, wherein said extractor is continuously maintained under an oxygen-free atmosphere throughout said loading, said extracting, said unloading and said repeating.
In addition, the invention provides a solvent extraction process comprising loading into an extractor a first batch including a feedstock and a solvent, extracting into said solvent a fat from said feedstock, unloading from said extractor said first batch after said extracting, and repeating said loading, said extracting and said unloading at least once, wherein said extractor is continuously maintained under an atmosphere consisting essentially of a vapor of said solvent throughout said loading, said extracting, said unloading and said repeating.